1. Field of the Invention
The invention relates to a compressor, and, in particular, to a compressor having improved thermal handling characteristics.
2. Description of the Related Art
A compressor receives a supply of fluid, such as a liquid or gas, at a first pressure and increases the pressure of the fluid by forcing a given quantity of the received fluid from a first volume into a smaller second volume using a piston assembly. Some compressors have a reciprocating piston that reciprocates within the cylinder to compress the fluid. The pistons may be connected to a crank shaft housed in a crankcase. The crankshaft may be operated by a motor housed in a motor housing. A typical piston assembly includes a cup seal to provide a seal between the pressurized and non-pressurized sides of the piston. The cup seal flexes during movement of the piston within the cylinder and the frictional engagement creates wear along the cup seal. The pressurization of gas on the pressurized side of the piston, the frictional engagement of the cup seal with the cylinder, and/or other operating conditions generate heat to which the cup seal is exposed. This heat further hastens failure of the flexible cup seal, thus limiting the life of the compressor.
In some compressors, heat may be dissipated from the cup seal using a crankcase that is directly coupled to the cylinder. Because of its mass, the crankcase may be intended to function as a heat sink to conduct the heat from the cylinder and the cup seal. Subsequently, a fan may provide air convection to dissipate the heat away from the crankcase.
However, in compressors where the motor housing is directly coupled to the crankcase, heat may be simultaneously conducted from the motor to the crankcase when heat is conducted from the cup seal and the cylinder to the crankcase. This is problematic when the thermal heat from the motor exceeds the heat being generated at or within the cylinder. In such situations, the heat from the motor may be indirectly conducted to the cylinder and the cup seal, thus ultimately increasing the heat on the cylinder and cup seal rather than decreasing it. Accordingly, further steps must be taken to remove heat from the cylinder/crankcase/motor housing system. For example, a larger fan may be used to provide higher CFM (cubic feet per minute) of air to convect the heat However, this may cause the device that includes such compressor and fan to be larger and bulkier. Alternatively or additionally, a larger crankcase may be used. However, this may cause the compressor to be bulkier, more expensive to manufacture, and inefficient.